The results indicate that the extracts increased the threshold of seizure in the MES model. It has been found that the drugs which raise the threshold for production of electrically-induced seizures are generally effective against absence seizures, where those that reduce the duration and spread of electrically-induced convulsions, are effective in Generalized tonic-clonic seizures . In addition to identifying against generalized tonic-clonic seizures, it has been proposed that the maximal electroshock test predicts anticonvulsant drug effects against partial seizures.
In Pentylenetetrazole (PTZ) induced convulsions the leaf, stem and root extracts of Coleus amboinicus increased the threshold of PTZ-induced convulsions in mice and offered protection against convulsion. In this model, the durations of convulsion in root extract was highest (7.07 min) than stem extract (5.21 min). Where as leaf extract has shown the lowest duration of convulsion (1.98 min). In addition, the recovery was 100% in all the animals tested with the extracts. Similarly the recovery time more in root extract (53.96 min) than stem extract (34.73 min) and it was minimum with the leaf extract (16.23 min). Whereas, the animals of control group, duration of convulsion was high compared to test drug treated animals, and all the animals showed mortality. Clonic seizures induced by PTZ is reported to be blocked by drugs that reduce T-type calcium current (Ethosuximide) and drugs that enhance inhibitory neurotransmission by GABAA receptors (Benzodiazepine, Phenobarbitone and Valproate) . Convulsants those actions previously unexplained (including penicillin and PTZ) may act as relatively selective antagonists of the action of GABA at GABAA receptors, the major inhibitory neurotransmitter which is implicated in epilepsy [17, 18].
The fact that the extracts protected the animals against PTZ induced seizures as well as delayed the occurrence of PTZ-induced convulsions. This may suggests that the three plant extracts contain compound(s) that facilitate GABA-aminergic transmission mechanism(s) to exert anticonvulsant effect by increasing the level of GABA.
It has been found empirically that drugs which inhibit PTZ induced convulsions are generally effective against absence seizures . Whereas those that reduce the duration of convulsions are effective in tonic-clonic seizures. The results indicates that the...